Abstract
The endophytic bacterial communities in tomato varieties having differing resistance (or susceptibility) to Ralstonia solanacearum were investigated using both cultivation dependent and independent approaches. Both approaches revealed the differences between resistant (Xiahong-1) and susceptible (Baoshi-5) cultivars in terms of diversity and abundance of endophytic bacteria. The amount of the endogenous bacteria in Xiahong-1 at different growth stages was significantly higher than that in Baoshi-5. Furthermore, there were more culturable and antagonistic endophytic bacteria in Xiahong-1 than that in Baoshi-5. Seven endophytic bacterial genetic groups were identified in Xiahong-1 by polymerase chain reaction- restriction fragment length polymorphism (PCR-RFLP) and 16S rDNA sequence, and they were highly similar to Sphingomonas yanoikuya, Pseudomonas pseudoalcaligenes, Serratia marcescens, Bacillus megaterium, Paenibacillus polymyxa, B. pumilus and B. cereus. Four groups were identified in Baoshi-1 which were highly similar to S. yanoikuyae, Pseudomonasfluorescens, Arthrobacter globiformis and Paenibacillus polymyxa. In addition, antagonistic endophytes were identified by 16S rRNA gene analysis, and tested for their abilities to protect tomato plants from infection with R. solanacearum. The relationships between plant resistance and endophytic bacteria diversity are discussed. Key words: Tomato, Ralstonia solanacearum, resistance, endophytic bacteria, diversity,biological control, 16S rRNA gene.
Highlights
Tomato bacterial wilt disease is an important tomato disease that is widely distributed in tropical, subtropical and temperate regions
Seven endophytic bacterial genetic groups were identified in Xiahong-1 by polymerase chain reaction- restriction fragment length polymorphism (PCR-RFLP) and 16S rDNA sequence, and they were highly similar to Sphingomonas yanoikuya, Pseudomonas pseudoalcaligenes, Serratia marcescens, Bacillus megaterium, Paenibacillus polymyxa, B. pumilus and B. cereus
The endophytic bacteria from tomato plant stems at the flowering period were isolated and incubated at 30°C for 4 days on NA plates
Summary
Tomato bacterial wilt disease is an important tomato disease that is widely distributed in tropical, subtropical and temperate regions. In China, the disease normally occurs at the flower and young fruit stages of tomato plant development, and there has been no effective control method to date (Liu and Zeng, 1999). R. solanacearum can live in the soil for a long time in non-hosts (Grey and Steck, 2001) which results in ineffectiveness for the control of bacterial wilt disease by crop rotation. The use of resistant varieties is thought to be the most effective way of controlling tomato bacterial wilt, the development of resistant varieties takes a long time and their use is limited by strain resistance specificity. Developing effecttive biological control agents is very important for the control of tomato bacterial wilt
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